Predicament: You've just summited a peak well above treeline on a blustery, overcast afternoon. As you follow a string of cairns down the ridge, the wind suddenly picks up, mixing spindrift and dense flurries into an opaque cloud that reduces visibility to nil.
Lifeline: Take a bearing with a compass or GPS and note your location on a map. Don't try to feel your way along a route; windblown snow can fill in contours, obscure cairns, and conceal drop-offs. Instead, seek shelter on the leeward side of a large boulder and mark your location with crossed trekking poles and a piece of bright fabric. Cover your mouth, nose, and eyes to block frigid air and blowing snow. Stay warm, dry, and hydrated while waiting for conditions to get better. When visibility improves, look for landmarks to guide your way down. Choose the quickest route to safety. If you must descend during a whiteout, follow a consistent heading and trust your GPS or compass; disorientation can cause people to wander in circles. If you begin to shiver uncontrollably or exhibit other signs of hypothermia, stop and seek shelter in order to re-warm your body.